Happy new month to my wife
That's so sweet! I'm happy to help you express your sentiment to your lovely wife. Here's a message you can use:
"Happy new month, my lovely wife! May this month bring us even more joy, love, and adventure together. I'm grateful for another opportunity to make more memories with you. Here's to a fantastic [month] ahead!"
Feel free to modify it to fit your personal style and relationship. I hope your wife loves it!